Kitchen Table Electronics Repair: Sherwood RX-5502 Multi-Zone Stereo Receiver скачать в хорошем качестве

Kitchen Table Electronics Repair: Sherwood RX-5502 Multi-Zone Stereo Receiver

I've been a big fan of the Sherwood RX-410x series of stereo receivers. My own units have proven reliable, but reports of trouble are out there and more frequent than they ought to be. I've wanted to know what goes wrong with these units, so I picked up a broken RX-5502 multi-zone receiver. Its circuitry differs somewhat from the RX-4105 or 4109 series, but the same basic design is used for power and preamplifier circuits. Sherwood claims a total output power (with all speakers going) rating of some 400 watts. They are dreaming! As found, this receiver would just shut down a few seconds after being powered up, followed by a blinking standby LED. Normally this indicates a power amplifier or power transistor fault, yet I did not think such a fault existed here. Watch and see how I did some troubleshooting and arrived at the cause of the problem. I'm not sure it's totally fixed yet, as the new regulator seems to be running awfully hot. I'll have to look into that some more, but it did survive running for several hours tonight. Now all I have to do is find some screws to replace the ones I didn't get with the unit and straighten out the cover a little bit. There are some interesting features that were never realized in this unit. When sold as a TEAC AG-980, this unit gains an optional serial port and some other connections. Sherwood's designer clearly thought about adding support to connect an iPod and support for DAB broadcast decoding. (You can see this in the video.) Outside of the things populated in the TEAC AG-980, I have no idea if these other artifacts were used. There is also the header for an optional RDS board, which I really want to find... Some Sherwood receivers have a self-test mode that can be helpful. This test usually just clears the memory, displays the firmware revision or illuminates every character in the display for a few seconds before shutting down. In this receiver, the display test remains on until the set is shut off, which came in handy while troubleshooting the power supply. To access the self test on an RX-5502, make sure the main power switch is on. Press and hold T/P Mode while pressing the "On/Standby" switch. The display will read "CLEARED". Immediately press the MEMORY to run the display test or show the firmware revision. (Note that this is not documented anywhere...I found it on my Insignia NS-R2000 first simply by pressing buttons. Not all of my receivers have it...my RX-4109 does not, while this and the RX-4105 do.)